The present invention is based on a method for shutting off a power tool when jammed, and a power tool.
Power tools with digital control are known. With mains-operated power tools, the voltage supplied to the drive motor is changed, e.g., via phase-angle control, while, with power tools powered by rechargeable batteries or batteries, pulse-width modulation is typically used to change the voltage. In various applications, a tool can easily become jammed in a work piece, which can result in rotational motion or “kick-back” of the power tool and a resultant loss of control of the power tool. Various systems and methods are known with which rotational motion and/or kick-back of the power tool that occurs when the tool becomes jammed can be prevented. Anti-rotation systems and methods are therefore known with which the course of rotational speed over time of the drive motor or the tool is evaluated as a function of time.
A power tool is made known in U.S. Pat. No. 4,267,914, with which the drive motor is shut off and/or a brake is activated when the rotational speed falls below a predetermined fixed or variable threshold value and a jam is therefore detected.